Age -related differences in the von Restorff isolation effect

Abstract

Older adults demonstrate poorer memory than younger adults on a variety of episodic memory tasks. In spite of this difference in overall level of performance, most manipulations of stimulus characteristics, encoding manipulations, and testing methods affect younger and older adults in similar manners. The limited data on the role of distinctiveness in memory, however, suggest that aging may be associated with a reduction in the benefit afforded by distinctiveness. In younger adults, memory for a unique item embedded in an otherwise homogeneous list is better than that for a control item, known as the von Restorff or isolation effect (von Restorff, 1933). Although this effect has been observed for younger adults, there seems to be no benefit for the isolated item for older adults (Cimbalo & Brink, 1982). ^ One explanation for this difference invokes Naveh-Benjamin's (2000) associative deficit hypothesis which attributes age-related differences in memory to a reduced ability of older adults to associate information in memory. According to this view, older adults will show memory deficits whenever they are required to form novel associations amongst units of information, such as associations between items or associations between items and contextual elements. ^ Experiment 1 tested younger and older adults using immediate free recall of lists of twelve unrelated nouns. Isolate lists contained one item presented in red font amongst 11 black items, and the control lists contained all black items. In Experiment 1, an isolation effect was obtained for both younger and older adults. Slower presentation rates did not eliminate age-related differences in the size of the effect. In Experiments 2 and 3, lists of categorized nouns were presented, with one semantically unrelated noun in the isolate lists. Both experiments failed to find an isolation effect for older adults when a semantic manipulation was used, despite equivalent levels of overall performance for younger and older adults (Experiment 2). These findings disconfirmed a prediction of the associative deficit hypothesis. Thus, the data on aging and the effects of isolation yield mixed support for the associative deficit hypothesis and suggest that older adults may sometimes view the isolate as a distraction. ^